input must be one of ('ba', 'zp')

Package:

8546

Exception Class:

ValueError

Raise code

    if kind == 'ba':
        ep = atleast_1d(roots(den)) + 0j
        tz = atleast_1d(roots(num)) + 0j
    elif kind == 'zp':
        ep = atleast_1d(den) + 0j
        tz = atleast_1d(num) + 0j
    else:
        raise ValueError("input must be one of {'ba', 'zp'}")

    if len(ep) == 0:
        ep = atleast_1d(-1000) + 0j

    ez = r_['-1',
            numpy.compress(ep.imag >= 0, ep, axis=-1),
            numpy.compress((abs(tz) < 1e5) & (tz.imag >= 0), tz, axis=-1)]

Links to the raise (1)

https://github.com/scipy/scipy/blob/e4b3e6eb372b8c1d875f2adf607630a31e2a609c/scipy/signal/filter_design.py#L101

Ways to fix

scipy.signal.findfreqs is used to find array of frequencies for computing the response of an analog filter. The parameter kind specifies whether the numerator and denominator are specified by their polynomial coefficients (‘ba’), or their roots (‘zp’). The valid value are:

"ba", "zp"

Steps to reproduce the error:

Install scipy

$ pipenv install scipy

$ pipenv shell

Run the sample code:

from scipy import signal
signal.findfreqs([1, 0], [1, 8, 25], N=9,kind="b")

Output:

---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-9-20ea5fdb42c8> in <module>()  1 from scipy import signal ----> 2 signal.findfreqs([1, 0], [1, 8, 25], N=9,kind="b") 
/usr/local/lib/python3.7/dist-packages/scipy/signal/filter_design.py in findfreqs(num, den, N, kind)  99 tz = atleast_1d(num) + 0j  100 else: --> 101 raise ValueError("input must be one of {'ba', 'zp'}")  102   103 if len(ep) == 0: 
ValueError: input must be one of {'ba', 'zp'}

Fixed version of the code:

from scipy import signal
signal.findfreqs([1, 0], [1, 8, 25], N=9,kind="ba")

array([1.00000000e-02, 3.16227766e-02, 1.00000000e-01, 3.16227766e-01, 1.00000000e+00, 3.16227766e+00, 1.00000000e+01, 3.16227766e+01, 1.00000000e+02])

Sep 23, 2021

kellemnegasi 31.6k

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